1. Field of the Invention
The present invention is directed to a clutch cover having a plurality of balance adjusting portions.
2. Discussion of the Background
A conventional diaphragm spring-type clutch assembly for an automotive vehicle includes an engine driven flywheel, a clutch cover secured to the flywheel, an axially reciprocable pressure plate held within the clutch cover and rotatable with the cover and flywheel, a clutch plate positioned between and adapted to be squeezed by the flywheel and pressure plate, a pivotal lever disposed outside of the cover for moving the pressure plate axially relative to the cover into and out of engagement with the clutch plate and a diaphragm spring pivotally mounted on the cover and compressed between the cover and the lever. The clutch cover is rotated with the flywheel. Thus, the clutch cover, and more particularly the whole clutch cover assembly including the cover, the pressure plate and the diaphragm spring, should be balanced relative to the rotational axis thereof. However, during the fabrication of the parts and/or the assembly thereof an imbalance is formed. In order to correct or reduce the imbalance of the clutch cover assembly, the weight and direction of imbalance are measured by an imbalance tester, and then a certain balance weight is fixed to or taken out of a certain peripheral portion of the clutch cover.
3. Description of the Prior Art
As methods for balance correction of a clutch or a clutch assembly, conventionally, methods as shown in FIGS. 14, 15 and 16 have been employed to thereby correct imbalance of the clutch at the final assembly process thereof.
(1) A predetermined peripheral portion of a clutch cover 2 as shown in FIG. 14 is caulked with a specified metal piece 101. (i.e. the piece caulking method) PA1 (2) A predetermined peripheral portion of a clutch cover 2 as shown in FIG. 15 is welded with a metal piece 102. (i.e. the piece welding method) PA1 (3) Holes 103 and 104 are made in a clutch cover 2 as shown in FIG. 16 at predetermined peripheral portions thereof by using a punch or a drill. i.e. the drilling method)
In these conventional clutch balance correction methods, according to the piece caulking method (1), caulking holes for pieces are suitably provided at predetermined portions of the outer periphery of the clutch cover and when the clutch is not in balance, one or more pieces have to be inserted into the caulking holes to be caulked to thereby attain balance. This caulking method requires an associated cost for the piece and it also involves a difficulty in carrying out automatic caulking to the clutch on the automatic assembly line of clutch.
According to the piece welding method (2), a predetermined-sized piece is welded at the lower portion of the outer periphery of the clutch cover. In this case, the cost of the piece is not neglected and automation thereof on the production line of clutch is also difficult.
The drilling method (3) is shown in FIGS. 17 and 18 in more detail. According to this method, a hole is made in the clutch cover 2 by means of a punch 105 and die 106 or a drill 107. In the case of punching, a punching force P of about 3 tons is required for a steel plate having a thickness of 3.2 mm. Therefore, the clutch cover 2 results in deformation due to such a large punching force P. To the contrary, in the case of drilling, chips 108 are produced and it is difficult to clear away the produced chips in the aftertreatment. Moreover, a long machining time is required for this method.